Showers of heavy isotopes including beryllium-10, are produced when cosmic rays, a high-energy mix of protons, electrons, and atomic nuclei from outside the solar system, collide with molecules in the Earth's atmosphere.Increased solar wind activity as the Sun moves towards solar max, reduces the amount of cosmic rays reaching Earth.

Time scales
By studying beryllium-10 levels in ice cores, scientists can determine the level of solar activity at a given time.

Drawing on two independent ice core records, Owens and colleagues modelled solar activity back to 1610, before the Maunder Minimum.

"Between 1650 to 1710 there were no sunspots recorded, even though there were lots of professional astronomers around at the time," says study lead author Dr Mathew Owens of the University of Reading in the United Kingdom.

"Yet despite the lack of sunspots, the Sun's magnetic field was still churning over its natural eleven-year solar cycle."